Wrap paramiko open_session() call in try/except

Ran across non-unix host where the call to paramiko's open_session() in
exec_command() would throw a EOFError exception.  This change wraps the
block in a try/except.

lib/ansible/runner/connection/paramiko_ssh.py

@@ -81,7 +81,13 @@ class ParamikoConnection(object):
         ''' run a command on the remote host '''
 
         bufsize = 4096
+        try:
             chan = self.ssh.get_transport().open_session()
+        except Exception, e:
+            msg = "Failed to open session"
+            if len(str(e)) > 0:
+                msg += ": %s" % str(e)
+            raise errors.AnsibleConnectionFailed(msg)
         chan.get_pty()
 
         if not self.runner.sudo or not sudoable: